CTLA4 and neoplasm: Further, CTLA-4-expressing FOXP3+ regulatory T cells (Treg cells), associated with an immune-suppressive function, were enriched in all tumor regions compared to normal mucosa (P = 0.012, P = 0.01 and P = 6 × 10−3 for superficial tumor, invasive margin and node; Fig. 3d), consistent with previous reports29.